System-wide protection, control, automation, metering, and monitoring of power transmission and distribution often requires the sharing of power system data among a plurality intelligent electronic devices (IEDs). A common reference point such as time is generally included, so that such data from the various IEDs may be properly compared.
For example, U.S. Pat. Nos. 6,845,333 and 6,662,124 (herein incorporated by reference) describe a relay system that obtains voltage and current values from a power line and uses a first sampling element to sample voltage and current signals at selected intervals of time. The resulting sampled signals are used for power system-wide protection, control, monitoring and metering. The sampled signals are then resampled at a rate that is a selected multiple of the power system frequency. The results of the resampling are used by processing circuitry to create processed power system data for protection functions including fault determinations.
In order to provide wide area protection, control, and monitoring systems, data (e.g., phasor data) associated with a power system acquired from the individual intelligent electronic devices (IEDs) is typically collected by a central processing unit where the data is stored (e.g., in non-volatile memory) and processed (e.g. resampled, time aligned, etc.) before being used in control, protection and monitoring logic, from which a control or protection command may be given. The result is that many of these existing systems require about 700 milliseconds before a control or protection command is issued.
Accordingly, one object of the present invention is to reduce the amount of time before a control or protection command may be issued.
Further, it is another object of the present invention to reduce the number of IEDs and central processing units (CPUs) needed in a wide area protection, control and monitoring system.